1. Field of the Invention
The present invention relates to a water-resistant regenerated collagen fiber containing a zirconium salt and a phosphorus compound, a method for producing the fiber, and a fiber bundle for hair including the fiber. More particularly, the present invention relates to a water-resistant regenerated collagen fiber suitable for use for hair, artificial fur, and the like, a method for producing the fiber, and a fiber bundle for hair including the fiber.
2. Description of Related Art
Regenerated collagen fibers are protein fibers that retain a distinctive molecular structure derived from collagen, and their feel, gloss, and texture are thus similar to those of human hair, a natural protein fiber with an extremely complex microstructure. For this reason, attempts have been made to use regenerated collagen fibers as fibers for hair and animal fur-like fibers such as artificial fur.
As raw materials of regenerated collagen fiber, animal skin and bones are generally used. Regenerated collagen fibers are produced by subjecting such raw materials to an alkali treatment or an enzyme treatment to obtain water-soluble collagen, and then extruding the water-soluble collagen into an aqueous inorganic salt solution to spin the collagen into regenerated collagen fibers. However, regenerated collagen fibers obtained in such a manner are soluble in water, and thus have poor heat resistance. Therefore, in order to make the regenerated collagen fibers resistant to water and heat, they are treated to be insoluble in water.
As ways to make the regenerated collagen fibers insoluble in water in order to provide the fibers with water and heat resistance, treating the regenerated collagen fibers with aldehyde compounds such as formaldehyde and glutaraldehyde, epoxy compounds, or metal salts such as chrome salt, aluminum salt and zirconium salt are known (Patent Documents 1, 2).
However, each of these treatment methods has problems to be solved. For example, when fibers are subjected to a formaldehyde treatment, free formaldehyde can be detected in the fibers, which leads to health problems. Further, when fibers are treated with various aldehydes and chrome salt, the fibers become strongly colored and are thus not suited for applications requiring light-colored fibers. Further, fibers treated with a zirconium salt do not become colored and have improved resistance to water and heat. However, due to having a shrinkage tendency believed to originate from zirconium, the fibers treated with a zirconium salt can shrink significantly when they are subjected to a wet-heat treatment, a treatment typically carried out when processing fibers into a hair ornament product, and this is problematic in terms of processibility. Further, the fibers treated with a zirconium salt shrink when the hair ornament product is subjected to a hair conditioner treatment, so that the hair style may change. Further, by combining an epoxy compound treatment and an aluminum salt treatment, light-colored regenerated collagen fibers can be obtained. However, as compared with human hair and animal hair that have keratin as the main component, these fibers have poor resistance to water and heat and are vulnerable to thermal damage when styling the fibers using a hair iron or a hair dryer (shrinkage in length, becoming curly or hard). Thus, they do not have satisfactory aesthetic properties. Note that the term “styling” as used herein refers to setting hair in a desired shape by heat at home, a beauty parlor or the like.
Further, attempts have been made to provide the fibers with improved resistance to water and heat by blending a thermoplastic resin with collagen as the raw material (see Patent Document 3). However, blending a thermoplastic resin with collagen leads to a coloration of the fibers, thereby impairing the regenerated collagen fibers' unique gloss and feel similar to those of animal hair.